Care supposedly rolled his ankle in training, although some reports have suggested the injury occurred on the way back from a training session and not during the session itself.
Ellis has therefore been recalled to the senior set up and will train with the first team for the remainder of the week.
If Care is ruled out of the Six Nations opener against the Azzuri, England team manager Martin Johnson will have to decide whether to throw Ellis straight back into the England starting team or to hand Northampton's Ben Foden his international debut.
His removal from the Saxons line up would see Paul Hodgson of London Irish move up to the starting XV, with Wasps youngster Joe Simpson taking Hodgson's place on the bench for the clash with Ireland A at Donnybrook on Friday night.
Elsewhere in the Saxons line up, Will Skinner, Chris Robshaw and Tom Guest form an all Harlequins back row, while capped internationals Nick Abendanon, Topsy Ojo, Danny Cipriani, David Paice and Jordan Crane all start, with the latter packing down at second row as opposed to usual position of No8.
George Skivington of Wasps skippers the side, with Quins wing David Strettle set to make his return to representative rugby as a replacement.
"Ireland will be a very tough opposition," said Saxons head coach and former Leeds Carnegie boss Stuart Lancaster.
"With so many new players in our squad, we'll be looking to build our team on and off the field and give the players a framework in which to express and enjoy themselves, yet still achieve our ultimate aim which is to win the game."
Nick Abendanon (Bath Rugby)*; Topsy Ojo (London Irish)*, Dominic Waldouck (London Wasps), Jordan Turner-Hall (Harlequins), Matt Banahan (Bath Rugby), Danny Cipriani (London Wasps), Harry Ellis (Leicester Tigers)* OR Paul Hodgson (London Irish)*; Matthew Mullan (Worcester Warriors), David Paice (London Irish)*, Dave Wilson (Newcastle Falcons), Jordan Crane (Leicester Tigers)*, George Skivington (London Wasps, captain), Chris Robshaw (Harlequins), Will Skinner (Harlequins), Tom Guest (Harlequins)
Replacements: Rob Webber (London Wasps), Dan Cole (Leicester Tigers), Stuart Hooper (Bath Rugby), Phil Dowson (Newcastle Falcons), Paul Hodgson (London Irish)* OR Joe Simpson (London Wasps), Stephen Myler (Northampton Saints), David Strettle (Harlequins)*
*denotes capped international